package com.lbc.pc;

/**
 *  线程之间的通信问题
 *  线程交替执行  a b  操作同一个变量  num = 0
 *  a  num+1
 *  b  num-1
 */
public class A {
    public static void main(String[] args) {
        Data data = new Data();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "A").start();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "B").start();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "C").start();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "D").start();
    }
}

//  等待，业务，通知
class Data {  //  属性、方法

    private int number = 0;

    //  + 1
    public synchronized void increment() throws InterruptedException {
        while (number!=0) {
            //  等待
            this.wait();
        }
        number++;
        System.out.println(Thread.currentThread().getName()+"==>"+number);
        //  通知其他线程，我+1完毕了
        this.notifyAll();
    }

    //  - 1
    public synchronized void decrement() throws InterruptedException {
        while (number==0) {
            //  等待
            this.wait();
        }
        number--;
        System.out.println(Thread.currentThread().getName()+"==>"+number);
        //  通知其他线程，我-1完毕了
        this.notifyAll();
    }
}
